Justinian is a strategic level board-wargame game set in the early 6th century, after the collapse of the Western Roman Empire and the burgeoning of the Byzantine Eastern Roman Empire. The Byzantine Emperor, Justinian I, has started his reconquest of the Western Roman Empire, and the game attempts to simulate his endeavor for players to emulate.

One player takes on Justinian's role, the other coordinates the Barbarian faction (basically the non-Byzantines); the designer also said the game can be played solitaire. The two factions' design are asymmetrical. Each turn, the Byzantine has to manage its finances, gaining income by taxing its controlled provinces and spending the money to raise and maintain its armies. Then the Barbarian and Byzantine factions alternate with each other to take actions (one at a time). They can raise more armies, move the troops, or do nothing. Whereas the extent of the Byzantine faction's orders are certainties, most of the Barbarian faction's are random; i.e. dice rolls sometimes determine how many armies join the Barbarians and whether these armies join the Byzantines instead. Both sides conquer territories by moving their armies into the lands. If two armies meet, combat occurs, which is resolved by dice rolls and cross checking the results with tables. The game features mutinies, naval actions, and random events. The latter throws up revolts, removal of generals and plagues.

The game ends after 10 turns or after a second plague has erupted. The Byzantine faction has to control a certain majority of the empire by that time to win. The game also ends if the reconquest was accomplished much earlier. If the Byzantine faction is unable to win when the game ends, the Barbarian faction is the winner.

JUSTINIAN is a game covering the reconquest of the Roman Empire by Justinian I, Emperor of Eastern Rome (Byzantium). Justinian’s reign represents Byzantium’s high water mark; his conquest of lands is exceeded in Roman history only by that of Augustus and Trajan.

Players. The game may be played by two players, or solitaire.[...]

—description from the rulebook